Several different mechanisms are known and used to operate the opening and closing of aircraft landing gear doors. However, most of these mechanisms have disadvantages associated with them because they can affect the overall performance of at least one of the aircraft landing gear doors, the landing gear and the aerodynamics of the aircraft.
Many door mechanisms are based on mechanical linkages that contain revolute and/or spherical joints. Such mechanical devices have the advantage of not including hydraulics which require additional maintenance, not including door proximity sensors and other electronic controls, and not requiring an emergency release system to be incorporated within them. In addition, mechanical linkages generally include fewer components than non-mechanical devices. Fewer components generally translates to a higher reliability for the device.
However, the use of mechanical linkages also includes several disadvantages. The use of such devices can inhibit landing gear extension and retraction due to door air loads since some devices make door closing when the landing gear is up and down quite difficult. In addition, the use of mechanical devices makes it difficult to control kinematics to perform the desired door opening and door closing sequence. The kinematics include such things as the speed of the door opening, the maximum angle the doors open, the timing with respect to how long the doors remain open while the landing gear moves by the doors.
It is therefore desirable to provide a door mechanism that retains the advantages of the mechanical linkages while overcoming some of the inherent kinematic problems.